blackAs shown in Figure REF , if the deployed model's characteristics (\(e\) ) could be identified and measured, the offline evaluation (\(Y\) )
would be independent blackof the confounderblack. Therefore, in order to blackvalidate the effect of closed loop feedback in a recommendation system (Hypothesis REF ), we have to quantify the deployed model's blackcharacteristics. To this end, blackfollowing [1]}, [2]}, we define the propensity score as follows:
